Revolver type firearm with interchangeable barrels and cylinders



Oct. 25, 1966 R LEWIS 3,280,495

K. REVOLVER TYPE FIREARM WITH INTERCHANGEABLE BARRELS AND CYLINDERSOrlgnal Filed Nov. 23. 1960 F' l@ I /08 'lh 'nl /oo 'f g- F IG 2 2 /08llo /8 50 54 40 /0 /4 /50 INVENTOF? KARI- R.. LEWIS ATTORNEYS UnitedStates Patent 3,289,495 REVOLVER TYPE FREARM WETH NTER- CHANGEABLEBARRELS AND CYLil DERS Karl R. Lewis, 77 Glney Rond, Wethersfield, Conn.Application Nov. i6, 1964, Ser. No. 411,470, which is a division ofappiication Ser. No. 71,339, Nov. 23, 196i), new Patent No. 3,163,951,dated Jan. 5, 1965. Divided and this application Dec. 8, 1965, Ser. No.512,363

4 Claims. (Cl. 42-59) This application is a division of my co-pendingapplication, Serial No. 411,470, filed November 16, 1964, now abandoned,for Firearm Barrel, Frame and Cylinder Construction. This latterapplication is in turn a division of my previous application, Serial No.71,339, filed November 23, 1960, for Firearm Firing Mechanism, nowPatent No. 3,163,951.

This invention reiates to firearms, and deals more particularly withimprovements in the construction of small firearms of the revolver type.

The general object of this invention is to provide a revolver-typefirearm which is readily and easily converted from a Constructionadapted for firing one size of cartridge to a construction adapted forfiring another size cartridge.

A more particular object of this invention is to provide a. firearm ofthe foregoing character including interchangeable barrels and cylindersfor the purpose of varying the size of cartridge fired by the firearm,the barrels, cylinders and other parts of the lirearm being soconstructed as to make impossible a dangerous mismatch of a smallcaliber barrel with a large caliber cylinder.

Gther objects and advantages or the invention will be apparent from thefollowing description and from the drawing forming a part hereof.

The drawing shows a preferred embodiment of the invention and suchembodiment will be described, but it will be understood that variouschanges may be made from the construction disclosed, and that thedrawing and description are not to be construed as deiining or limitingthe scope of the invention, the claims forming a part of thisspecification being relied upon for that purpose.

Of the drawing:

FIG. l is a side view of a firearm embodying the present invention; and

FIG. 2 is a side View of the firearm shown in FIG. l with the upperportion thereof being shown in vertical longitudinal section and withthe lower portion being shown in elevation with the grip pieces removedfrom the frame.

Referring now to the drawing, there is shown a iirearm embodying theinvention and of the revolver pistol type. The iirearm comprises a framewhich is provided with a mechanism cavity 12, a cylinder recess 14 and acrane recess 16 in the upper portion thereof. Between the mechanismcavity 12 and the cylinder recess 14 is a transverse or intermediatewall 18, and a longitudinal bore 2@ extends between the crane recess 16and the mechanism cavity 12. The mechanism cavity l2 has one side wall22 which is integral with the other portions of the frame. The outersurface of this wall is shown facing the viewer in FiG. 1. The otherside wall of the mechanism cavity is provided by a removable side plate,not shown, which is attached to the side of the frame facing the viewerin FIG. 2 by means of screws or other fasteners. Removal of the sideplate provides access to all of the parts of the firing mechanism shownin FlG. 2.

The lower portion of the frame includes a trigger guard 24 ofconventional configuration and a depending grip S Patented Get. 25, 1966portion 26 located rearwardly of the trigger guard. As shown in FIG. l,the grip portion of the frame comprises two generally downwardlyextending arms 28, 28 that are spaced apart longitudinally of the frame.The arms 28, 28 have attached thereto, two vside pieces, one of which isshown at 30 in FIG. l, which are located one on either Side of the frameand which are preferably made of wood or plastic. These side pieces,together with the grip portion of the frame, constitute the grip of thefirearm, the grip being hollow to provide a storage chamber for holdingextra cartridges or other articles. Access to the storage chamber isprovided by a pivotal lioor plate 32, as shown in FIG. 2, which ispivotally connected adjacent its rear end to the grip portion 26 andwhich at its forward end is provided with a releasable latch 34. Thelatch 34 normally holds the oor plate in closed position with respect tothe storage chamber and is manually operable by a thumb or finger torelease the ioor plate for swinging movement away from the grip portion.

A crane 36 is attached to the frame 1t) for outward swinging movementabout an axis extending longitudinally of the frame. This mounting ofthe crane to the frame is obtained by providing the crane with a pivotalportion 38 which is loosely received by the longitudinal frame bore 26.As viewed in FIG. 1, the crane 36 is swingable outwardly about the axisof the longitudinal bore 2G in a direction toward the viewer from theposition shown. Swinging movement of the crane in a direction away fromthe viewer in FIG. 1 is limited by engagement of the crane with the sidewall of the crane recess. This side wall is not shown in FIG. l, but islocated immediately behind the crane and is integral with the frame.

A cylinder 40 of somewhat conventional construction is rotatably securedto the crane for rotation about an axis extending longitudinally of thefirearm. Normally, the cylinder 40 is positioned within the cylinderrecess 14 as shown in FIGS. 1 and 2, but it is swingable outwardlytherefrom with the crane 36 in order to displace the cylinder to an openposition located to one Side of the frame for loading and ejectingpurposes. The cylinder 49 includes a plurality of cartridge receivingchambers 42, 42 which are shown empty in FIG. 2. When the cylinder is inits normal position, the intermediate wall 18 of the frame and theflanges 44, 44, one of which is formed on either side of the framebehind the cylinder, at least partially close the rear ends of thecartridge chambers 42, 42 to prevent the addition or removal ofcartridges to or from the chambers; however, when the cylinder is swungoutwardly from the frame, the rear ends of the cylinder cartridgechambers are positioned away from the wall 18 and the adjacent ange 44so that cartridges may be removed or added.

The cylinder 49 is rotatably secured to the crane 36 for rotation aboutan axis extending longitudinally of the frame. As shown in FIG. 2, thecylinder mounting means includes a sleeve 46 which is fixed to the crane36 and extends rearwardly therefrom through the center of the cylinder4t). The outer surface of the sleeve 46 fits loosely with the centerbore of the cylinder 4i? to permit the cylinder to rotate about thesleeve. An ejector rod 4S is received within the sleeve 46 and islongitudinally slidable relative thereto, the sleeve 46 at its forwardend having a reduced diameter section which engages and slidablysupports the ejector rod. At its rear end, the ejector rod 4S isprovided with a conventional cartridge extractor 5d which is movablerearwardly to eject the cartridges from the cylinder when the cylinderis disposed in its open position to the side of the frame. In ejectingthe cartridges, the ejector engages the rims of the cartridges in thecartridge chamber and moves them rearwardly and out of the chambers. Theejector rod 43, it will be noted, extends fonwardly beyond the crane 36and this forwardly extending portion of the rod is movable rearwardly bythe user to effect a rearward cartridge eje-cting movement of thecartridge extractor. The ejector rod 4S and the cartridge extractor arenormally held in the forward positions shown in FIG. 2 by a compressionspring 52 which is located in the bore of the sleeve 46 and which at oneend engages an abutment S4 in the cylinder 40 and on its other endengage-s an ejector rod collar 56 carried by the ejector rod 48.

The cylinder 4t) is normally held in the closed position illustrated inFIGS. l and 2 by means of a cylinder bolt 58 `which has a rearwardportion slidably received in the lbore 6@ of the cartridge extractor andin the bore of a sleeve 62 fitted into the intermediate frame wall 18,and a forward portion slidably received in the bore 64 of lthe ejectorrod 48. The cylinder bolt 58, as shown in FIG. 2, includes an integralcollar 66 which is normally held in the rearward position shown by aspring 68. A means provided for moving the cylinder bolt 58 forwardly tounlock the cylinder from the frame for outward swinging movement thereofcomprises a cam element 70 that is pivotally connected to the frame 10for pivotal movement about a transverse axis between active and inactivepositions. Ori its periphery, the cam element 7i? has two closely spacedfaces 72, 72 and two widely spaced faces 74, 74. In its inactiveposition, the cam element 70 is positioned as shown in FIG. 2 so thatone of the closely spaced faces 72 faces the hammer 76 while Ithe otherface 72 engages a cylinder bolt release member 78 which has its forwardpart positioned in the sleeve 62 and in engagement with the rear end ofthe cylinder bolt 58, the cylinder bolt 58 under the action of its bias-urging the cylinder bolt release mem-ber 73 rearwardly and intoengagement with the carn element 70. As shown in FIG. 2, the hammer 76is engageable with the firing pin 80 when the cam element 7) is in theinactive position shown. The cam element 70 is moved to an activeposition by rotating it approximately 90 about its transverse axis fromthe position shown in FIG. 2. This brings one of the widely spaced faces74 into opposing relation with the hammer 76 and causes the other face74 to hold the cylinder bolt release member 7S in a forward position atwhich the cylinder bolt 58 is held out of the sleeve 62 so that thecylinder is freed for lateral swinging movement. The spacing of thefaces 74, 74 is such that the face which opposes the hammer 76 isengageable with the latter to hold it slightly rearwardly from itsneutral position and to thereby prevent or block it from engaging thefiring pin 80. The cam element '70 therefore in addition to serving as apart of the releasing mechanism for the cylinder also serves as a safetydevice for the rearm. Movement of the cam element 70 from its active toits inactive position, is produced by manual operation of a lever 82located on the outside surface of the rearm as shown in FIG. 1, thelatter being connected with the cam element 7G which extends through theside wall 22 of the mechanism cavity 12. With the lever 82 in theposition marked F as shown in FIG. l, the cam element 70 is disposed inits inactive position so as to permit the hammer to engage the firingpin to cause firing of a cartridge, while with the lever in the positionmarked S in FIG. 1, as shown -by the broken lines, the cam 70 is in itsactive or safety position at which position the hammer is blockedagainst firing engagement with the pin and at which the cylinder bolt isreleased from the frame to permit lateral outward movement of thecylinder. At both the S and F positions of the lever 82 the frame 10 isprovided with an indent, such as shown at 84 in FIG. 1, which cooperateswith the lever to releasably hold it in the position to which it ismoved.

Referring to FIG. l, it will also be noted that the llange 44 located onthe side of the frame from which the cylinder 40 swings is provided witha cam surface 86 which engages the rear end of the cylinder bolt S andcams the same forwardly as the cylinder is swung from its open positionback to its normal closed position. When the Cylinder is in its openposition, it is held in place on the sleeve 46 by a blocking element 88which is connected with the frame and has a forwardly facing surfacethat abuts the rear face of the cylinder to restrain its rearwardmovement.

The cylinder 40 is releasably held in a fixed angular position withrespect to the frame 'by a cylinder stop 90 having a head 92 which isengagea-ble `with any one of several cylinder notches 94, 94 which areformed in the outer surface of the cylinder and arranged in an annularseries. The number of notches 94, 94 corresponds to the number ofcartridge chambers 42, 42 and the notches are so located that when thecylinder stop 92 is in locking engagement with a notch 94, acorresponding cartridge chamber 42 will be in proper operativerelationship with the firing pin which is located in the intermediatewall 18.

The barrel 96 of the rearm is located in front of the cylinder 4t) andhas a threaded rear portion 93 which is received in a correspondingthreaded opening in the frame 10. The barrel, of course, is so locatedwith respect to the frame and the cylinder 46 that the longitudinal axisof its bore is in alignment with the longitudinal axis of the upper oractive chamber 42 which is held in firing position by the cylinder stophead 92. The forward end of the barrel 96 is provided with a radiallyoutwardly extending flange 100. A shroud 102 surrounds the barrel 96 andextends substantially the entire length of the barrel from the forwardend face of the frame to the barrel flange 103. The shroud 102 has abore 104 for receiving the barrel which bore conforms closely to theoutside surface of the barrel, but with a sufficiently loose t existingbetween the barrel and the shroud as to permit the barrel to slidelongitudinally and angularly of the shroud during assembly ordisassembly of the firearm. The shroud 102 is held longitudinally inplace on the barrel by means of engagement with the forward face of theframe 10 at its rear end and `by means of engagement with the barrelflange 11N) at its other end. Angular displacement of the shroud withrespect to the frame is prevented by means of a locking pin 106 whichextends between the frame and the shroud and which is preferably locatedbelow the 'barrel as shown in FIG. 2. In FIG. 2, .the partial sectionillustrating the locking pin 106 is taken on a plane located in front ofor closer to the viewer than the plane on which the remainder of theview is taken. The upper front portion of .the shroud 102 is providedwith a front sight 108 which is preferably formed integral with theshroud, and a rear sight 110 is attached .to the rear portion of theframe 10 as shown in FIGS. 1 and 2.

As best shown in FIGS. 1 and 2, the shroud 102 also includes alongitudinally extending recess 112 formed in one side thereof forreceiving the ejector rod 48 when the crane 36 and the cylinder 40 arein their normal closed or -ring positions with respect to the frame.Adjacent the forward end of the recess the shroud is provided with abore 114, FIG. 2, which receives a spring 116 and a ball 118, the springurging the ball rearwardly as shown and the -ball being retained lin thebore by the shroud being staked adjacent the mouth of the bore. The ball118 extends partially from the bore 114 and normally engages the forwardend -of the eject-or rod 48, the mouth of the bore 64 of the ejector rodforming a detent for receiving the ball. The spring loaded ball 118therefore serves as a support for the forward end of the ejector rodwhen the cylinder is in closed or ring position.

The tiring mechanism of the tiring arm is located in the mechanismcavity 12 and is described in detail in my above-referred to patent towhich reference is made for a more detailed description thereof. For thepresent, it is sufficient to note that in addition to the hammer 76 themechanism includesv a trigger 120 which is supported for pivotalmovement relative to the frame 10 by a pivot pin 122. The trigger 120 ismovable in a conventional manner between forward and rearward positionsrelative to the frame and connected with the hammer is a means,indicated generally at 124 for controlling the movement of the hammer inresponse to the movement of the trigger. The trigger is biased in thecounterclockwise direction, as viewed in FIG. 2, so that the lowerportion thereof is normally held in the forward position illustrated.This bias for the trigger is provided by a connecting pin 126 which ispivotally connected to the upper portion of the trigger 120 `and whichextends forwardly into a bore 128 formed in the pivotal portion 38 ofthe crane 36, there being provided in the bore 128 a helical compressionspring 130 and a spring guide 132 which serve to engage the forward endof the connecting pin 126 and to urge it rearwardly. The spring guide132 is slidably received in the bore 128 and extends forwardly throughthe center lof the spring 130 to prevent the spring from buckling orbending in the transverse direction. The rear end of the spring guide132 is provided with an enlarged head having a forward face which abutsthe spring 130 and a rear face which abuts the connector pin 125, thelatter face preferably being provided with a depression for receivingthe forward end of the connector, as illustrated. The spring 130 and theconnector pin therefore function tc normally hold the lower portion 0fthe trigger in the illustrated forward position and to oppose itsmovement to the rear.

In accordance with this invention, the firearm as illustrated lis sodesigned that both the barrel 96 and the Icylinder 40 may be replacedwith other barrels and cylinders to adapt the rearm for use withcartridges of different calibers. As mentioned previously, and as shownin FIG. 2, the barrel 96 has a threaded rear portion 98 whi-ch isreceived in a corresponding threaded bore formed in the frame forwardlyof the cylinder recess 14. Also, the shroud 102 which surrounds thebarrel 95 has a loose t therewith so that the barrel may slide angularlyand longitudinally relative to the shroud during assembly anddisassembly of the barrel with the shroud and frame. Therefore, thebarrel may be quickly removed from the frame and shroud by unscrewing itfrom the frame, the barrel flange 19t) prefera-bly having a hexagonalcross section to permit the application of a Wrench thereto for thepurpose of rotating the barrel when threading or unthreading it withrespect t-o the frame. Also, after the barrel 96 is disassembled fromthe frame and shroud, the crane 35 may be disconnected from the frame byswinging the cylinder from its recess 14 and then sliding the craneforwardly to remove the pivotal portion 38 thereof from its frame bore20. Once the crane is removed from the frame, the cylinder 4t) may beremoved from the crane by sliding the cylinder rearwardly with respectto the sleeve 46. Thus, both the cylinder and the barrel may be removedfrom the firearm to permit their replacement by another cylinder andbarrel, respectively, to change the caliber of the fire- "arm, therebeing provi-ded in association with the firearm various matched sets ofcylinders and barrels for this purpose. That is, there is provided aplurality of barrels generally similar yas shown at 95 but havingdifferent cal-iber bores, together with a corresponding plurality ofcylinders, similar to that shown at 40, each of which is adapted for usewith a particular one of said barrels and which is provided withcartridge chambers dimensioned lto receive cartridges having a calibersimilar t-o that of the bore of the barrel with which the cylinder isassociated. Therefore, each time a barrel is replaced with a differentcaliber barrel, the cylinder is yalso replaced with a new cylinder whichcorresponds in caliber with that of the new barrel.

The procedure for attaching a new barrel and cylinder to the firearm i-ssubstantially the reverse of the procedure used for removing the oldbarrel and the old cylinder. That is, the new cylinder is positioned onthe sleeve 46 while the crane 36 is detached from the frame 10, then thecrane is connected to the frame by positioning the pivotal portion 38thereof in the frame bore 20, and then the cylinder is swung into itsrecess. Then the shroud 102 is positioned in front of the frame 10 andthe crane 36 with the locking pin 106 positioned between the frame andthe shroud and with the shroud bore in alignment with the threadedbarrel-receiving bore of the frame. The new barrel is then slidlongitudinally into the barrel bore and rotated in the proper directionto thread the rear portion thereof into connected relationship with thethreaded frame bore and to bring the barrel flange into tight engagementwith the forward face of the shroud 102 so that the shroud is heldfirmly in place between the forward face of the frame and the barrelflange 100.

As a precautionary measure, the relative sizes of the variousinterchangable cylinders and barrels are preferably such as to makeimpossible the matching of a small caliber barrel with a large calibercylinder. In FIGS. l and 2, which show a barrel matched with a cylinderof the proper size, it will be noted that the rear portion of the barrelextends rearwardly beyond the rearwardly facing wall of the cylinderrecess 14, as at 152, and is positioned in closely spaced relationshipwith the forward face of the cylinder 40. The distance which the barrelextends rearwardly beyond the rearwardly facing wall 150 of the cylinderrecess is predetermined and is made to vary with the size of the barrelbore so that a barrel having a small -caliber bore will extendrearwardly beyond the wall 15) a greater distance than a barrel having alarger caliber bore. Likewise, the various cylinders 4t? are ofdifferent lengths so that when properly matched with the propercorresponding barrel, the close spacing between the forward face of thecylinder and the rear face of the barrel will be maintained. Thus, acylinder having cartridge chambers dimensioned to receive large calibercartridges will have a longer longitudinal length than a cylinder havingcartridge chambers dimensioned to receive cartridges of a smallercaliber. From this, therefore, it will be evident that in the event asmall caliber barrel were to be connected with the firearm at the sametime as a larger caliber cylinder the forward face of the cylinder wouldbe disposed at a location forwardly at the rear face of the barrel.Therefore, the barrel would interfere with the cylinder to prevent thecylinder from being swung to its normal operating position in thecylinder recess 14 and thus the firearm would be rendered inoperative inthe event such a potentially dangerous mismatch between the barrel andthe cylinder occurred. If the cylinder, prior to attaching the barrel,is in place within the recess 14, the mismatched smaller bore barrelwould be tightened against the front face of the -cylinder to bind itsaction and thereby to prevent operation of the firearm. If a smallerycaliber cylinder is put in place with a larger caliber barrel, the guncan be shot, but in this case a smaller caliber bullet will pass throughthe larger bore barrel, and in this case only minor accuracy will belost and no danger will be involved.

The invention claimed is:

1. The combination in a firearm of: a frame, means defining a `cylinderrecess in said frame having forward and rear walls and a bore in theforward wall for receiving the rear portion of a barrel, crane means forreleasably receiving a cylinder and for supporting the same in saidcylinder recess for rotation about a longitudinal axis, a plurality ofbarrels of differing caliber bores which barrels are selectivelyconnectible with said frame and have rear portions which are receivablein said frame bore, and a cbrresponding plurality of cylinders which areselectively connectible with said crane and each of which cylinderscorresponds with a respective one of said barrels and has a plurality ofcartridge chambers dimensioned to receive cartridges of a caliber`similar to that of the corresponding barrel bore, each of said barrelswhen in connected relationship with said frame having the rear portionthereof extending rearwardly beyond the rear face of said forward framewall by a predetermined distance which distance depends on the caliberof the barrel bore and is greater for a small caliber bore barrel thanfor a larger caliber bore barrel, and each of said cylinders having apredetermined length which depends on the caliber of the cartridgesreceivable by its cartridge chambers and which length is greater whenthe chambers are dimensioned to receive larger caliber cartridges thanit is when the chambers are dimensioned to receive smaller calibercartridges so that if a cylinder having chambers dimensioned to receivea larger caliber cartridge is connected to said crane at the same timeas a barrel having a bore smaller than said last dimensioned calibersaid cylinder will interfere with the rear end portion of said barrel toprevent said cylinder and crane from being moved to proper tiringposition with respect to said crane.

2. The combination defined in claim 1 further characterized by all ofsaid barrels having forward portions of substantially equal length andof substantially the same outside diameter and each barrel including agenerally radially extending rearwardly facing surface spaced forwardlyfrom its rear end portion, and a shroud 'having a bore adapted toreceive a selected one of said barrels which shroud bore is of such asize and shape as to conform closely to the outside surfaces of saidbarrels while permitting a barrel to slide longitudinally and angularlywith respect thereto during assembly and disassembly of said shroud withany one of said barrels, said shroud including a generally radiallyextending forwardly facing surface and being held in place on a selectedbarrel by engagement with said frame at its rear end and by theengagement of said rearwardly facing barrel surface with said forwardlyfacing shroud surface at a point spaced forwardly from said frame.

3. The combination defined in claim 2 further characterized by saidframe bore being internally threaded and each of said barrels havingexternal threads on its rear portion for threaded connection with saidframe bore, the

engagement of the rearwardly facing surface on the connected barrel withthe forwardly facing shroud surface limiting the threading movement ofsaid barrel relative to said frame in the tightening direction toaccurately locate the rear end of said barrel relative to said frame.

4. The combination in a firearm: a frame, means deining a cylinderrecess in said frame having forward and rear walls and a bore in theforward wall for receiving the rear portion of a barrel, means forreleasably receiving and supporting a cylinder in said cylinder recessof said frame for rotation about a longitudinal axis, a plurality ofbarrels of different caliber bores which barrels are selectivelyconnectible with said frame and have rear portions which are receivablein said frame bore, and a corresponding plurality of cylinders which areselectively connectible with said releasable receiving and supportingmeans and each of which cylinders corresponds with a respective one ofsaid barrels and has a plurality of cartridge chambers dimensioned toreceive cartridges of a caliber similar to that of the correspondingbarrel bore, Y

each of said barrels when in connected relationship with said framehaving the rear portion thereof extending rearwardly beyond the rearface of said forward frame wall by a predetermined distance whichdistance depends on the caliber of the barrel bore and is greater for asmaller caliber barrel bore than for a larger caliber barrel bore, andeach of said cylinders having a predetermined length which depends uponthe caliber of the cartridges receivable by cartridge chambers and whichlength is greater when the chambers are dimensioned to receive largercaliber cartridges than when the chambers are dimensioned to receivesmaller caliber cartridges so that when any one of said barrels isconnected with said frame the space remaining in said cylinder recess isinsutiicient to properly accommodate a cylinder having chambersdimensioned to receive cartridges of larger caliber than that for whichthe bore of the connected barrel is dimensioned.

No references cited.

BENJAMIN A. BORCHELT, Primary Examiner.

1. THE COMBINATION IN A FIREARM OF: A FRAME, MEANS DEFINING A CYLINDERRECESS IN SAID FRAME HAVING FORWARD AND REAR WALLS AND A BORE IN THEFORWARD WALL FOR RECEIVING THE REAR PORTION OF A BARREL, CRANE MEANS FORRELEASABLY RECEIVING A CYLINDER AND FOR SUPPORTING THE SAME IN SAIDCYLINDER RECESS FOR ROTATION ABOUT A LONGITUDINAL AXIS, A PLURALITY OFBARRELS OF DIFFERING CALIBER BORES WHICH BARRELS ARE SELECTIVELYCONNECTIBLE WITH SAID FRAME AND HAVE REAR PORTIONS WHICH ARE RECEIVABLEIN SAID FRAME BORE, AND A CORRESPONDING PLURALITY OF CYLINDERS WHICH ARESELECTIVELY CONNECTIBLE WITH SAID CRANE AND EACH OF WHICH CYLINDERSCORRESPONDS WITH A RESPECTIVE ONE OF SAID BARRELS AND HAS A PLURALITY OFCARTRIDGE CHAMBERS DIMENSIONED TO RECEIVE CARTRIDGES OF A CALIBERSIMILAR TO THAT OF THE CORRESPONDING BARREL BORE, EACH OF SAID BARRELSWHEN IN CONNECTED RELATIONSHIP WITH SAID FRAME HAVING THE REAR PORTIONTHEREOF EXTENDING REARWARDLY BEYOND THE REAR FACE OF SAID FORWARD FRAMEWALL BY A PREDETERMINED DISTANCE WHICH DISTANCE DEPENDS ON THE CALIBEROF THE BARREL BORE AND IS GREATER FOR A SMALL CALIBER BORE BARREL THANFOR A LARGER CALIBER BORE BARREL, AND EACH OF SAID CYLINDERS HAVING APREDETERMINED LENGTH WHICH DEPENDS ON THE CALIBER OF THE CARTRIDGESRECEIVABLE BY ITS CARTRIDGE CHAMBERS AND WHICH LENGTH IS GREATER WHENTHE CHAMBERS ARE DIMENSIONED TO RECEIVE LARGER CALIBER CARTRIDGES THANIT IS WHEN THE CHAMBERS ARE DIMENSIONED TO RECEIVE SMALLER